In order to save transportation costs, a housing structure of rear projection type television receivers is designed to package individually a screen, a casing separated between an upper part and a lower part, a back cover and the like, thereby achieving the smallest possible volume as a whole. In addition, there is provision for dismounting the screen easily to facilitate maintenance services such as screen replacement and the like.
Therefore, the housing structure of the prior art projection type television receivers whereby video images are optically enlarged and projected on a light transmission type screen comprises a cabinet with a plurality of bosses formed on the periphery of the front opening thereof and with a plurality of bosses formed inside of the rim of the back thereof and a back cover with screw pits formed on the rim thereof.
The light transmission type screen is fixed to the inside of the cabinet's rim by means of thrusting members before the back cover is put in place.
FIG. 17 is a perspective view of a prior art projection type television receiver.
FIG. 18 and FIG. 19 show detailed structures of part of the back of the foregoing projection type television receiver.
In FIG. 18 and FIG. 19, a screen 21 is pressed against the inside of the front surface's rim of a cabinet 23 by means of thrusting members 22.
The thrusting members 22 are fixed to a plurality of bosses 23b, which are formed on the inside periphery of a front opening 23a and the rest of the front surface of the cabinet 23, and bosses 23c, which are formed inside of the rim of the back of the cabinet 23, by means of screws 24. In order to reinforce the corners of the cabinet 23, "U" letter shaped reinforcing members 25 are fixed to the bosses 23c by means of screws 26.
FIG. 19 shows how the reinforcing members 25 are mounted on the bosses 23c of the cabinet 23 by means of the screws 26.
As illustrated in FIG. 17, the prior art casing is fixed to the casing's lower part 29 from the upper back thereof before a back cover 27 is put in place.
FIG. 20 is a cross-sectional view of the area where the back cover 27 is put together with the cabinet 23.
In FIG. 20, the back cover 27 provided with screw pits 27a is fixed to the cabinet 23 mounted on the casing's lower part 29 through the bosses 23c formed on the back of the outer rim of the cabinet 23 by means of screws 28.
Thus, the prior art cabinet made of resin is structured in such a way that maintenance and checks including replacement of screens and the like are performed only after the back cover 27 is removed.
Therefore, with large screen projection type television receivers of the conventional structure as described in the above, the work of screen exchange, maintenance and checks requires a removal of the back cover when scars are formed on the screen surface and checks are found necessary due to a long period of screen use. When it comes to replacing a screen, it is necessary first to remove the back cover 27 and then follows a work to remove screws 24 from the back of the casing carried out entirely inside of the cabinet 23. For the above work, the whole television receiver has to be moved to make a sufficient space. As a result, it has not been easy to carry out the foregoing maintenance work such as screen exchange and the like in terms of time and man power.
Moreover, during the course of assembly work in the factory and also at the time of delivery, the cabinet and back cover are attached to the housing structure only after the screen is put in place, thus resulting in problems of increased work steps and reduced productivity. In addition, the world-wide interest in environmental issues requires products that facilitate recycling of the materials used in the products. From this point of view, the conventional projection type television receivers are not readily dismantled for further steps of material recycling.
Furthermore, with the cabinet of the prior art structure, it is difficult for the existing resin molding technology to produce a heavy wall thickness that is required to keep a sufficient mechanical strength for the opening at the side of the cabinet where the back cover is attached. Because of this problem, reinforcement metal fixtures are used to maintain a sufficient strength without incorporating a heavy wall thickness in the cabinet.